The IEM (in ear monitors) Bible thread - a guide to help every musician

[TimR]

I don't think your brain would notice ears being out of phase as that happens all the time with sounds arriving at one ear before the other. 

[Al Krow]

16 hours ago, TimR said:

I don't think your brain would notice ears being out of phase as that happens all the time with sounds arriving at one ear before the other. 

 

Thanks Tim. Makes sense! 

 

On 10/01/2026 at 17:31, TimR said:

Page 69.

Alt Out (CQ-20B)

The Alt Out provides an alternative balanced TRS output connection. Source – Select any other Output or route the Listen out.

 If Listen is set, when no Listen button is pressed, the Alt Out will be sourced from Main LR.

 Listen is sent to the Alt Out at full volume for use with IEM systems that have input level control. For adjustable level, the headphone output should be used. 

 

I've had at a look at the manual reference and the two Alt Out sockets are for the CQ-20B model only (not present on my model the CQ-18T). "Listen mode" simply changes the mix to be some as FoH (ie sourced from Main LR). It won't change the nature of the Alt out from being balanced TRS to stereo TRS though, which is the point we seem to have moved on to. Although the manual is does seem to imply that using balanced TRS with IEM systems is fine.

 

If it makes an "in principle" difference, I guess it would be best practice to be using the silver TS to TRS adapters as standard rather than the gold TRS to TRS adapters (per pic at bottom of previous page)? And this is a more general point?

 

Those plugging their 1/4" stereo jacks from their wireless IEMs (eg Swiff WX520) into a single balanced mono aux-out jack will just have to take what they get!

 

@Woodinblack be good to get your trained electrical engineering hat on this!

 

Edited Monday at 11:14 by Al Krow

[Woodinblack]

14 hours ago, TimR said:

I don't think your brain would notice ears being out of phase as that happens all the time with sounds arriving at one ear before the other. 

 

It would be exactly the same as the sound coming entirely from one side, ie 90° to you, but somehow being as loud on the back side

 

 

14 hours ago, Al Krow said:

If it makes an "in principle" difference, I guess it would be best practice to be using the silver TS to TRS adapters as standard rather than the gold TRS to TRS adapters? 

 

What is a TRS to TRS adapter? Why would you need to adapt that?

 

14 hours ago, Al Krow said:

Those plugging their 1/4" stereo jacks from their wireless IEMs (eg Swiff WX520) into a single balanced mono aux-out jack will just have to take what they get!

 

if you plug a mono lead in, it would be fine, its only with a stereo lead. Thats one advantage of a balanced output, it would give you a fine mono output if you use a TS jack.

[SimonK]

Was procrastinating and wondering about the difference between dBu and dBV was this morning. The following article is really interesting and especially the table at the end that touches on an issue that comes up time and again in amp threads.

 

https://www.soundonsound.com/sound-advice/decibels-explained

 

[Al Krow]

1 hour ago, Woodinblack said:

It would be exactly the same as the sound coming entirely from one side, ie 90° to you, but somehow being as loud on the back side

What is a TRS to TRS adapter? Why would you need to adapt that?

if you plug a mono lead in, it would be fine, its only with a stereo lead. Thats one advantage of a balanced output, it would give you a fine mono output if you use a TS jack.

 

Thanks Woody - the TRS to TRS is simply a 1/4" to 3.5mm TRS adaptor - please see the pic in my last but one post (bottom of previous thread page). Seems to make no difference using that vs using a TS a TRS adaptor - but that may just be us not being overly impacted by the phase issue?

 

I think what you're saying is best practice would be to use the TS to TRS adaptor (the silver one in the same pic)?

 

And what this discussion has also made me realise is that if we want to transition to getting stereo for our IEMs e.g. with the Swiff WX520 - the A&H CQ-18T has two stereo headphone outs that could be assigned to providing this for two members of the band. We then have a further 6 balanced mono outs, some of which can be paired to provide additional stereo IEM feeds for those that want it (obviously not an option for the Xvive U4 users). That's definitely an additional worthwhile take-away from this chat! 

 

Edited Monday at 11:11 by Al Krow

[MichaelDean]

There has been some talk in my band of potentially investing in an IEM setup with an XR18. What's the best way of combining the two XLR outputs to one TRS jack cable?

[dave_bass5]

37 minutes ago, MichaelDean said:

There has been some talk in my band of potentially investing in an IEM setup with an XR18. What's the best way of combining the two XLR outputs to one TRS jack cable?

I have one of those cables that i occasionally run in to a P2. You could also use the headphone out with just a standard stereo jack cable.

Edited Monday at 10:30 by dave_bass5

[Woodinblack]

1 hour ago, Al Krow said:

I think what you're saying is best practice would be to use the TS to TRS adaptor (the silver one in the same pic)?

 

Yes.

 

1 hour ago, Al Krow said:

. We then have a further 6 balanced mono outs, some of which can be paired to provide additional stereo IEM feeds for those that want it (obviously not an option for the Xvive U4 users). That's definitely an additional worthwhile take-away from this chat! 

 

 

indeed - that's what mine are (as I have balanced TRS outs on the X18)

 

 

For normal mono outs, I have TRS to XLR adapters, and I do have a dual XLR mono to XLR stereo cable (or a few of them) that I could use, they usually are with the chapman stick that has a stereo out. 

 

- edit - I note that this is now actually OTT, as I could go from the stereo ¼" jack to the ¼" jack on the IEMs - its just I have these cables anyway as I was using the MS-2 before hand, and that only had a 3.5mm jack

[Phil Starr]

15 hours ago, Al Krow said:

 

Hmmm...

 

We've got balanced mono aux outputs as previously noted.

 

We've got and used a 1/4" TS to 3.5mm TRS adapter jacks (the lower silver jack in pic) to allow us to plug in to the desk to deal with the issues that Woody mentioned.

 

What stumps me though is why we're getting equally good results with 1/4" TRS to 3.5mm TRS stereo adapters (upper jack), with standard IEM headphones with standard 3.5mm TRS jacks?! So we're using either without issue.

 

 

 

My coffee time teaser for today   (mainly because I'm not 'allowed' to do Wordle)

 

So the first thing to understand is that balanced line signals have an earth that is at 0V and two other signals +ve and -ve. The two signals go up and down at the same time but when + is going up - is going down. When the signal gets to the amp a transformer or a bit of electronics turns this back to an unbalanced signal.

 

In a jack the tip should be +ve and the sleeve is the earth the ring should be -ve and inside the jack socket there are three sprung contacts that touch the plug when it is connected. Many jack sockets also have switches built in operated whenever a plug is inserted, so this can complicate the wiring. If you use the mono jack (the bottom one) then the - and the earth connectors in the socket are both touching the sleeve and are short circuited. What happens next depends upon the grounding arrangements. Since it is working for you then there are no issues. It doesn't work on my Flow 8 for example unless I only insert the plug halfway.

[Al Krow]

3 hours ago, Woodinblack said:

 

Yes.

 

 

indeed - that's what mine are (as I have balanced TRS outs on the X18)

 

 

For normal mono outs, I have TRS to XLR adapters, and I do have a dual XLR mono to XLR stereo cable (or a few of them) that I could use, they usually are with the chapman stick that has a stereo out. 

 

- edit - I note that this is now actually OTT, as I could go from the stereo ¼" jack to the ¼" jack on the IEMs - its just I have these cables anyway as I was using the MS-2 before hand, and that only had a 3.5mm jack

 

Thanks Woody. Amusingly I have the exact same red-white dual TS -> single stereo TRS jack adaptor, which I use to feed Spotify tracks to the desk from my PC at home (or phone at a gig between sets), into the stereo input of the CQ-18T. Makes sense that you can use the exact same bit of kit to combine two balanced mono aux outs -> stereo jack of your IEM. Obviously plugging directly in a single stereo TRS headphone out achieves the same thing and we are fortunate to have two of those on the CQ-18T.

 

I've actually got a couple of those silver 1/4" -> 3.5mm TRS jacks (in my pic on the previous page of this thread) and will make those the default for us where we are using single Aux-Out balanced mono -> stereo TRS IEM jack.

(In fact, just ordered an extra few spares, because they don't last forever! In case useful for anyone else - you can get 3 from Kenable for under £4 inc. P&P)

 

As @Phil Starr has rightly pointed out, and which completely ties in with my own experience from a full year of gigging with the A&H CQ18T, many desk aux-outs should easily be able to provide enough output for headphone users to directly plug into the desk and hear themselves clearly and easily. If yours doesn't, you may need the assistance of a headphone amp (like the Behringer P2). But best practice when plugging a stereo IEM jack directly into an Aux balanced-out, to avoid phasing and other issues, is to use one of those Kenable-type TS -> TRS convertors.

 

Right I think that's me sorted! Really appreciate, as ever, the BC collective-wisdom on this and I now understand a bit better why our current setup has been working so well, particularly when old rules applying to older tech might caution against! Back to the fretboard...

 

Edited Monday at 14:46 by Al Krow

[Muzz]

On 08/01/2026 at 09:41, Woodinblack said:

 

I have never actually ever had a problem with the MS-02, just they feel a bit flakey, and on mine the power button is not the best (it works, but its like if you push it too much it goes off again). I think they are a great system for the price (wish the stereo / mono and on/off buttons were further apart!) and I will keep them as a backup

 

 

My channels aren't linked, I never got round to it, I just use 5 and 6 as a pair, and set them manually as I want them. 

 

On 08/01/2026 at 10:19, dave_bass5 said:

Can you not do it yourself in whatever app you are using, or do you mean he doesn’t want it done?

The drummer and I are locked out of everything but our individual Aux channels on the mixer app...it's his mixer, y'see...

[Muzz]

On 08/01/2026 at 12:26, Al Krow said:

 

That's a very tidy haul, Muzz - congrats! (And hopefully you're not about to tell me that bookings were down 40% and it was actually a really crap year for you guys!)

 

Are you guys doing a mixture of pub and function work or predominantly doing one or the other?

Pubs, pubs, pubs...the odd beer festival (I think a couple last year), but yeah...pubs...

[Chienmortbb]

2 hours ago, Al Krow said:

 

Thanks Woody. Amusingly I have the exact same red-white dual TS -> single stereo TRS jack adaptor, which I use to feed Spotify tracks to the desk from my PC at home (or phone at a gig between sets), into the stereo input of the CQ-18T. Makes sense that you can use the exact same bit of kit to combine two balanced mono aux outs -> stereo jack of your IEM. Obviously plugging directly in a single stereo TRS headphone out achieves the same thing and we are fortunate to have two of those on the CQ-18T.

 

I've actually got a couple of those silver 1/4" -> 3.5mm TRS jacks (in my pic on the previous page of this thread) and will make those the default for us where we are using single Aux-Out balanced mono -> stereo TRS IEM jack.

(In fact, just ordered an extra few spares, because they don't last forever! In case useful for anyone else - you can get 3 from Kenable for under £4 inc. P&P)

 

As @Phil Starr has rightly pointed out, and which completely ties in with my own experience from a full year of gigging with the A&H CQ18T, many desk aux-outs should easily be able to provide enough output for headphone users to directly plug into the desk and hear themselves clearly and easily. If yours doesn't, you may need the assistance of a headphone amp (like the Behringer P2). But best practice when plugging a stereo IEM jack directly into an Aux balanced-out, to avoid phasing and other issues, is to use one of those Kenable-type TS -> TRS convertors.

 

Right I think that's me sorted! Really appreciate, as ever, the BC collective-wisdom on this and I now understand a bit better why our current setup has been working so well, particularly when old rules applying to older tech might caution against! Back to the fretboard...

 

You should really have some type of protection in a 3.5mm stereo jack plug (TRS) to 5.35mm mono jack (TS) I put 100 ohm resistors in as I worry the headphone outs may not like signal being fed back into them. 

[Al Krow]

1 hour ago, Chienmortbb said:

You should really have some type of protection in a 3.5mm stereo jack plug (TRS) to 5.35mm mono jack (TS) I put 100 ohm resistors in as I worry the headphone outs may not like signal being fed back into them. 

 

I guess I don't worry as much as you about these things, as it's never been an issue for us to date. Our lovely KZ ZARs (£30 from Ali Express) getting trodden on / lost, on the other hand, seems to be a more regular occurrence! But given they cost no more than a set of bass strings, I'm pretty relaxed and, let's be honest, I lack anything close to your expertise to do anything about it anyway!! 

 

Edited Monday at 17:23 by Al Krow

[Al Krow]

@Woodinblack just following up on the Swiff WX520 and a couple of online comments (summarised by Google), given this is on our band shopping list as a 5.8 GHz wireless.

• Real-world latency is often much higher than advertised (e.g., 10ms vs. 5ms claim).
• Exhibits a noticeable high-frequency roll-off (from 6kHz) and increased distortion above 4kHz, making it sound dull. 

Does the first of those tie up with your experience - is it something you can test?

I guess the second is not going to be more of an issue for guitarists than us bass players, but may impact female vox if it's an issue?

 

 

[TimR]

10ms is the equivalent of 3.4m away from your speakers. It will depend what else you have in the chain.

 

[SimonK]

6 hours ago, Al Krow said:

@Woodinblack just following up on the Swiff WX520 and a couple of online comments (summarised by Google), given this is on our band shopping list as a 5.8 GHz wireless.

• Real-world latency is often much higher than advertised (e.g., 10ms vs. 5ms claim).
• Exhibits a noticeable high-frequency roll-off (from 6kHz) and increased distortion above 4kHz, making it sound dull. 

Does the first of those tie up with your experience - is it something you can test?

I guess the second is not going to be more of an issue for guitarists than us bass players, but may impact female vox if it's an issue?

 

 

 

I have a set arriving today from Thomann and intend to check them out over the weekend so will let you know first impressions. Mind you they were so (relatively) cheap I figured best to just try them rather than dive in at the £400/500+ end of the market!

[Woodinblack]

7 hours ago, Al Krow said:

Real-world latency is often much higher than advertised (e.g., 10ms vs. 5ms claim).

 

When I get a chance I will test that to see what it is.

 

7 hours ago, Al Krow said:

• Exhibits a noticeable high-frequency roll-off (from 6kHz) and increased distortion above 4kHz, making it sound dull. 

 

Cetainly doesn't sound dull (and I have bright strings) and I haven't noticed a distortion, although honestly when gigging I am not going to be that concerned about a 6khz roll off, this doesn't have to be hifi

[BigRedX]

2 hours ago, TimR said:

10ms is the equivalent of 3.4m away from your speakers. It will depend what else you have in the chain.

 

But that doesn't take the way your brain processes audio in an acoustic space into account. They would only be the same if you and your speakers were in an extremely dead acoustic space. 

 

In the real world the way your brain uses your ears and eyes, being 3.4m away from your cab in a typical room is not the same is having the sound piped directly into your ears with a 10ms delay.

[Greg Edwards69]

I see that Xvive have a new stereo version of the venerable u4 system coming. Looks like you plug it into left and right XLR from the mixer.

Edited 1 hour ago by Greg Edwards69

[Woodinblack]

28 minutes ago, Greg Edwards69 said:

I see that Xvive have a new stereo version of the venerable u4 system coming. Looks like you plug it into left and right XLR from the mixer.

 

 

That makes sense. Surprised they didn't do it earlier really, I would have certainly looked at it when I was replacing my broken U4, and later when looking for a replacement for the MS-2.

[Al Krow]

2 hours ago, BigRedX said:

 

But that doesn't take the way your brain processes audio in an acoustic space into account. They would only be the same if you and your speakers were in an extremely dead acoustic space. 

 

In the real world the way your brain uses your ears and eyes, being 3.4m away from your cab in a typical room is not the same is having the sound piped directly into your ears with a 10ms delay.

 

Smooth-hound wireless, when it was market leader, back in the day, was 5ms to 8ms, if I remember correctly. Can't recall if that was ever an issue for most of us?

I think the point folk did make was the cumulative nature of latency when adding the impact of pedals.

 

49 minutes ago, Greg Edwards69 said:

I see that Xvive have a new stereo version of the venerable u4 system coming. Looks like you plug it into left and right XLR from the mixer.

 

It's the next but one successor U4 (mono 2.4 GHz) -> U45 (mono 5.8 GHz)-> U45D (stereo 5.8 GHz) i.e. giving the benefit of 5.8 GHz and stereo, and I guess partly in response to the Swiff WX-520 coming on the scene. It will likely be 2 to 3 times the price of the Swiff though i.e. £200+ for the U45D vs around £80 for the Swiff (on Ali Express).

 

In addition the Swiff would appear to be a neater set-up, without that cumbersome external second balanced-mono input to achieve stereo. Hmmm...I already think I know which system I'll be heading down when it comes to upgrading my U4 😅

 

Edited 54 minutes ago by Al Krow